Particle Size Distributions of Airborne Particulate Matter in a Ferrosilicon Smelter

Abstract

Dust and fume emissions are a prominent issue in the ferroalloy industry and relevant to both indoor air quality, occupational exposure and outdoor air quality and other environmental effects. Exposure assessment with respect to respirable particles and “total dust” have been demanded from the authorities for years. Recently the focus has widened and exposure assessment focusing on ultrafine particles is in demand. In this study, ultrafine particles are studied in a ferrosilicon smelter. In order to understand the prevalence of ultrafine particles in the workplace environment, five different locations in the production hall were selected and the number concentration and the particle size distributions were investigated by use of stationary instruments. The worker attendance at each location was logged, so that the exposure at each location could be evaluated in accordance to attendance time. Number concentrations for the time periods where workers were present could be calculated. The locations selected were: tapping area, casting area, ladle transport corridor, control room and electrode-weld-on”. The measurement equipment used was a Nanoscan SMPS from TSI, measuring the particle size range 10-420 nm. The dominating size in the tapping areas is 205.4 nm for both furnaces and one SAF has an additional peak is at 11.5-15.4 nm. In the ladle transport area, the dominating particle sizes are 15.4 nm, 27.4 nm and 154 nm. The casting area has a bimodal size distribution and the two peaks are at 15,4 nm and 154 nm. The electrode welding area is very different from the other areas investigated here. The concentrations are significantly higher and the dominating size is 205.4 nm, but with substantial increased contributions in the range 86-365 nm. This paper discusses the findings and explores possible explanations behind the particle size distributions with support in the literature. Different dust and fume sources present in a smelter are discussed.